


A Lesson In Combustion

by keelywolfe



Series: by any other name [59]
Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), Alternate Universe - Underswap (Undertale), Established Relationship, Fluff, M/M, Someone Is Keeping Secrets..., Spicyhoney - Freeform, Underfell Papyrus (Undertale), Underswap Papyrus (Undertale), Undertale Monsters on the Surface, hints of angst, papcest - Freeform
Language: English
Status: Completed
Published: 2019-03-10
Updated: 2019-03-10
Packaged: 2019-11-15 02:10:36
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,564
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18064571
Author URL: https://archiveofourown.org/users/keelywolfe/pseuds/keelywolfe
Summary: Stretch loves doing experiments with the local rugrats and Edge loves to help. But there seems to be a shadow hanging over their fun and Edge doesn't mean the ones under Stretch's sockets.





	A Lesson In Combustion

* * *

It couldn’t be called spring, not really. Despite the bright sunshine, the temperature was too cold to have worked its way past winter and the world was still positioned in that uncertain place between seasons where the weather hadn’t quite managed to free itself from the persistent clutches of the previous one and made its way to the next. 

None of that seemed to bother any of Edge’s companions, not his husband nor any of the children who were gathered excitedly around them, listening eagerly while Stretch explained. 

“…when we ignite the fuel, it causes a mini-explosion. pressure builds up rapidly and once it overcomes resistance, the expanding gas will force the obstruction down the barrel…”

Edge couldn’t be sure how much of that the children actually understood, but they were hanging on his every word. A collection of wide-eyed minions enamored by the grandeur of science. Well, Edge was pretty sure it was science; Stretch was in charge of this mission and the only goal Edge had was to keep property damage to a minimum. 

That and the pleasure of watching as Stretch gestured excitedly while he talked. There was a pretty, hectic flush to his cheek bones and a certain familiar gleam in his eye lights. That sight alone made trekking out to the outskirts of town carrying all their supplies worth it. 

“okay, are we ready? all rugrats stay behind the line and don’t think i don’t see you trying to creep closer, henry.” A hand settled on Edge’s back and Stretch leaned in to murmur, “hold on tight, babe, it’ll have a little kick.”

“I have it.” Edge held the pipe securely to his shoulder. Behind him, he heard the rasp of a lighter. Moments passed, the gathered assembly nearby holding their collective breaths and then…

_Foom!_

The pipe bucked in his hands but stayed pointing at the sky. From the end emerged a dark blur, launching up and up into the air. The children around them cheered excitedly as reached its peak and began tumbling downward until finally a fluff of white appeared and opened, the barely visible outline of a doll dangling beneath a parachute that drifted slowly towards the ground.

“and there we have it,” Stretch said cheerily. He pushed back a pair of oversized goggles that wouldn’t have been out of place on an air ship from the fantasy books Edge secretly enjoyed. “that’s how a combustion chamber works! anyone want to see again?”

A chorus of ‘yes’ and ‘please’ rose up in a tangle around them, every child begging for a repeat performance. Their goggles were cardboard rather than safety plastic and they’d each made their own pair earlier that day. Stretch had assured him they were only for the aesthetic and wouldn't really be necessary for this experiment.

Even budding mad scientists needed to keep up appearances and not all of them had the required amount of arms needed for a white lab coat. 

“okay, then run and get our hero, kiddos! bring back our pilot and we’ll give it another round.” All of them scurried off in the direction of the falling parachute and Stretch flopped to the ground next to where Edge was crouched with a groan. “if i could figure out a way to siphon even a fraction of that energy, we’d never need another patent.”

“That’s still quite a run for them,” Edge said. He set the potato cannon gingerly on the ground and wondered, not for the first time, what it had to do with potatoes. 

Better to ask when the children were here; Stretch always did well explaining to an audience and that allowed Edge to pay less attention to the words and more to his husband. It was a small indulgence and Edge took it whenever he could. 

Stretch shrugged. He was writing something in a small notebook that looked like a series of complicated calculations, then flipped it shut and stuck it in his hoodie pocket. “eh, it’s good for them. besides, i bet none of them have a problem falling asleep tonight. their parents will thank us.”

“I’m sure their parents would have plenty to say to us, but I’m not sure a thank you would be among them. Exhausting their children for them is more a bribe than a reward.” 

Speaking of exhaustion…Stretch often looked like he was two steps from a nap, but he didn’t usually look so weary. Today, despite the excitement of experimenting, he seemed to be abnormally tired; there were orangish smudges beneath his sockets, a few shades darker than his magic, and it hadn’t escaped Edge’s notice that Stretch was sitting down whenever there was a place for it.

Coming out here this morning had been Stretch’s idea, but even now he was settled cross-legged on the ground, heedless of the cold or any damp, using his lighter for a cigarette instead of his so-called potato cannon. 

“Are you all right?” Edge asked. He was torn between dragging Stretch into his lap to keep him off the cold ground and propriety. Not that any of the children would do more than groan at any displays of affection but there were appearances. “You seem tired.”

“well, someone has been keeping me from my usual beauty sleep,” Stretch leered at him.

Not untrue, but…”I’m sorry, love. I know you need your rest.”

“…what?” Stretch blinked, smoke trailing from his nasal passage before he coughed it out, “wait, no, i’m kidding, you’re fine, babe. if i didn’t want to, i’d say so.”

“You would.” Edge didn’t allow it to be a question. Stretch dropped his cigarette, crushing it out before it was more than partially burned through and scrambled over to hug him tightly. It sent him close to tumbling into Edge’s lap and Edge gave up, pulling him in entirely. Propriety could wait for another day. 

“of course i would!” Stretch told him, fiercely. He curled up into Edge’s embrace, clinging. “i like sex, babe, and i like you and the two combined is like mixing coffee and honey ice cream. the best of all worlds.”

He supposed that made sense in the tangle of Stretch’s thoughts. Gently, he stroked a thumb beneath Stretch’s socket, over that lingering darkness. “All right. Then why don’t you take a nap when we get back home?”

Only to be taken aback when Stretch jerked away from the touch and glared at him with narrowed sockets. “i’m fine.”

“All right,” Edge said, mildly. His patience with any coddling was paper-thin today, it seemed. Stretch had been remarkably tolerant with having Edge at home all week, to the point of indulgence, and Edge certainly didn’t blame him for finally reaching the end of his endurance. 

Almost instantly, Stretch’s irritation crumpled. He sagged down into Edge’s arms. “no, i’m sorry, you’re right, i am tired.”

He caught Edge’s hand and pressed it back to his cheek bone. Obediently, Edge stroked again, his fingertips gently tracing, and if he was discreetly testing Stretch’s temperature, there was no reason to bring it up. “You don’t need to apologize, love, I’ve survived worse. I’m not trying to tell you what to do, I’m only concerned.”

Stretch looked away and there was _something_ , a fleeting expression that crossed his face made Edge narrow his own sockets. What—

The baying of approaching children cut off his thoughts and Stretch squirmed free, scrambling to his feet. 

“hey, guys,” Stretch said cheerily. “okay, here is where important decisions are made! mama bear here made us some snacks—”

“Stretch…” Edge sighed, trying to impart dire warning in that single word. It really wasn’t surprising that any warning was blithely ignored. 

“—so we can have those, or we can launch our guy again first. what’s the verdict?”

“Snacks!” Almost in unison, a few of the children even clapped their hands in delight. His snacks were almost as popular a diversion as an experiment and Edge couldn’t help a faint smile. 

“Excellent, I brought bran muffins—” The stifled groans made him struggle harder to hide a smirk. “Ah, my mistake. It was chocolate chip cookies.”

The resulting cheer was loud enough to make him wince and, thus redeemed, he opened the container and parceled out the correct allotment of cookies per child. Stretch was standing back, watching him with a smile of his own…and far enough away to keep Edge from prodding at him. 

This wasn’t over, by far, but for the moment Edge relented and while the children ate their treat with more or less the expected manners, he helped Stretch reload the potato cannon.

“Why is it called a _potato_ cannon?” Edge asked, idly. As expected, Stretch’s eye lights lit up.

“oh, well, the concept is for a combustion launcher, the potato part is about the ammo—” He warmed to the subject quickly for his audience, his lecture wandering off the beaten path down trails about different kinds of ammunition that could be used, along with cautionary tales about various kinds of combustion.

Edge watched him as he talked. The way his hands moved, the growing flush in his cheekbones. His enthusiasm lighting fuses in all the little scientists at his feet. He drank that all in, the lovely sight of his husband at his best. 

That and the visible shadows lurking beneath Stretch’s sockets. 

He wasn’t about to forget those. 

-finis-


End file.
